Standard reference materials are of great usefulness, both for instrument calibration and for the interpretation of complex spectra. By understanding the spectra of each component making up a system, justifiable conclusions can often be drawn about the multicomponent system. The categories of standard substances under investigation are: self-assembled monolayers, poly(amino acids), proteins, "ordered" protein surfaces, polysaccharides, plasma-deposited surfaces, and conventional polymers. All reference materials must meet a number of criteria. They must be of high purity and possess a well-defined stoichiometry. They must also be stable upon storage as well as under low energy electron and X-ray flux. Finally, the information obtained should be generally useful in the interpretation of spectra originating from NESAC/BIO projects.